Heat gun on mainboard

[Grossel]

Hi.

I'm sitting on a place where I haven't got a vacuum tin pump (not sure about the correct english terminology on certain tools, I hope you can bear with me) and I do have a mainboard that I want to dismount some components. Mainly some caps.

So here I am, without proper soldering tools. But I do have a heat gun that can deliver enough temperature to melt tin. As a consequense of this, any components and components close will heat up until the tin melts and I can drag the wanted component out from the mainboard.

The question I have is what components have the greatest chance to survive this threatment and what type of components will almost for sure die?


Thanks

 

[JimB]

I haven't got a vacuum tin pump (not sure about the correct english terminology

I think you mean a "de-soldering tool", often referred to as a "solder sucker".

But I do have a heat gun ...
...The question I have is what components have the greatest chance to survive this threatment and what type of components will almost for sure die?

I have sometimes used a heat gun to remove components from a circuit board, the only thing which usually does not survive is the circuit board itself.
If you want a quick and dirty way of recycling components, use a heat gun.
If you are trying to remove components from a board which you want to repair and re-use, do not use a heat gun.

Many years ago I saw a tip in a magazine, the guy held the old board over a bowl of water and heated the solder side of the board with a blow lamp
The components were supposed to drop out of the board and into the water to cool them.
An interesting idea but most components are held in place by a slight bend in their legs.

JimB

 

[Inquisitive]

Translation of "blow lamp", please. Not a term I'm familiar with.

 

[JimB]

Translation of "blow lamp", please. Not a term I'm familiar with.

Blow torch in USA English.

Have a look here for picture of a traditional blow lamp.
https://en.wikipedia.org/wiki/Blow_torch

The same expression could also be applied to the modern equivalent where a burner is screwed directly to a small canister of propane/butane.

Where the burner is on the end of a flexible hose which connects to large gas cylinder, then we would probably call the burner a torch, rather than a lamp.

JimB

 

[Inquisitive]

Thank for the definition of blow lamp. We seem to have lost touch with our mother tongue and colloquialisms.

 

[Grossel]

I've just using my heat gun on a atx motherboard

Hi.

Now I have some experience of using a 2000W (package claim 300/600 degrees celsius) Cotech heatgun, and I will try to share the experience as good as I can here.

First of all, Don't try to do this in your house where you live. You think that the smell of a regular solder iron is bad? Using a heat gun probably produces at least ten times more smell.

The advantages compared to a little solder gun should be obvious. I can tell from my experience the cons and pros.
Pros
* You'r able to get components and contact with a large number of pins off the printboard.
* 2000W is really an overkill when the job is to get out one single cap that fill the repair need of another computer, but it gets the job done.
* The component legs is often more clean - the small tubes that connect the paths within different layers stays in the wholes. This have previous being a problem when using a solder iron on components with multiple pins.
* It's really easy to pill off smd components too - just heat the spot on the oposite side on the print board.
* If the goal is to pill off all solded components on a mainboard, it's far more efficient than using a solder iron.
Cons
- If used to pilling off smd components, the nearby paths often get loose before the component itself. So that effectly kills a print board.
- Nearby components is likely to fall off, since the heat gun cannot heat just a little spot on the printboard.
- Cannot avoid grilling nearby plastic parts - wich gives a really bad smell.
- Giving the above cons, a heat gun cannot be used to "fix" a printboard.


I'll also tell about my experience about the different types of components and their ability to survive.
Caps
I haven't tested the caps to see it they work so I cannot really tell at this time. Ill I know for sure is that they got loose without any particular problems.
I beleive most of the caps did survive because the rate of the heat should be more gentle than for a solder iron, as both legs are heated up simultaneous and it takes more time for the solder tin to melt.
Inductors
Nothing to tell. Just be careful with the polygrip tool and avoid damage to the winding insulation. Since two legs is heating up almost simoustanely a flat screwdriver can be used to pill the inductor off the board.
I guess the same can be said about resistors, but the motherboard didn't had any regular resistors.
BCD led display
To be onest, I thaught that it wouldn't work and the housing would melt and get loose. But, it did work and the display looks like coming straight from the production line. Success.
Main power connector (made of plastic)
This was one of the thing I just HAD to try, even if I was almost sure that the plastic housing would melt and that it would be just a mess of melted plastic and baked-in pins.
But, it turns out to work as the plastic house around the atx pins actually survived the temperature. Not only did it survive, but the plastic house is not deformed at all. I probably had my luck here as all of the pins came loose pretty fast. If one or more pins refused to get loose the plastic housing would probably not survived and get deformed.
Big connectors such as stereo jack outputs and usb/nic housing
Worked lie a charm. But, it takes much more heat to get a big connector loose than a single cap. Espechially as the casing metal is conducting heat wery efficient. Because of the need to use of exessive heat, nearby components as caps, inductors etc will fall off before the connector.
USB connector
This is the only connector that does NOT survive the heat as it is used another type of plastic that doesn't stand the heat.
Fan connector (3 pins)
This connector introduce a new problem. The polygrip tool will often have a good grip on two pins, but not the third. As a result, only two pins get loose while the last one is still stucked to the printboard. Holding the polygrip very tight will solve this in most cases.

Another thing I had to test while I was outdoor with heatgun and mobo. Some of the inductor with external housing was close to the cpu socket where the back side of the printboard was covered by plastic foam (or what it is called).
Exept from a lot of bad smell from melted plastic I got the inductors loose without any problems.

 

[RODALCO]

I use a 1500 Watt heatgun for component recovery and it works very well. Don't hold the nozzle too close and circle around component solder pads, which you need to get off the board, like multipin IC's. Often they drop out when the board is given a little tap.

It works also great for removing flyback transformers, inductors etc. from old TV circuit borads.

 

[Nixie]

I use a $15 heat gun from Aldi that claims 400 C temperatures.

This is my method and tools:
Heat gun, vice, elastic, crocodile clips, tweezers.

The vice holds the board.

I recover specialized components with the heat gun and use a length of elastic attached to a crocodile clip which grips the component. The other end of the elastic is anchored to a magnet which is stuck to the vice.

I heat the solder side of the board and the component, when it is ready, is just pulled away by the elastic.

There's not much tension on the elastic so the component does not go far and the component comes away at the quickest time with minimum heat.

Crocodile clips on elastic for medium size components and anything tiny gets the tweezers and I close the tweezers up with a rubber band so the tweezers are tight around the tiny component. As before, I use elastic attached to the inside of the tweezer and the component is gently pulled away.

For ICs I use an IC-puller attached the same way.

 

[Grossel]

Nixie, I'm not very familiar with the english name of tools, but I always figure what is what.

I cannot figure what the elastic is. Is it some kind of metal anchor with multiple joints that keeps the crocodile clip?

 

[Nixie]

Grossel, the elastic is simply the same stuff that is in your underwear to keep your underwear up!! It is a stretchy cord that is elastic (stretches but goes back to original shape).

To remove the component, a crocodile clip is attached to the component, an elastic cord is attached to the clip and the other end of the elastic is stretched and attached to an anchor-point.

Apply the heat-gun and when the solder melts, the elastic cord pulls the component out of the board.



By the way, thanks for your very nice description of component removal.

 

[Grossel]

LOL, I was first thinking on that but dismissed that since I figured that a rubber band will toss the component far away from the table where you sit. But that's the way you do it, yes
I would like if you had a picture (I might have got this all wrong).

I will add something I figured out when trying to get off smd chips. I figured that if I could heat the backside of the board (heat gun heats the opposite side of the board than the smd's is mounted) I could reduce the area on the board when tin is melting and by that avoid other smd's also get loose.
It didn't work very well because the conducting paths tends to be loose before the tin on the smd's melted. So in order to keep the print board intact, I found that I had to apply heated air directly on the smd's.

 

[Nixie]

I've removed SMDs from the component side by gently heating with the heat-gun, but using a tiny nozzle.

SMDs are built to take some heat so I don't worry too much about that. When I am removing components I look at my clock on the kitchen wall which has a seconds hand and I try to 'learn' each PCB and the amount of heat it will take to remove components.

Also I have a sharp, long stainless tool which has a pointy bit at the end and I use this to poke at the soldered joints nearby to determine when the solder is melting.

About the elastic, it only has a small amount of tension on it so that the component doesn't go far. Also the tweezer or clip that is grabbing it is much heavier so it tends to just fall to the bench.

On the elastic band I have a 'tensioner' so that the tension on the elastic is adjustable. You know those little devices on a backpack that allows you to adjust an elastic cord's tension by having a hole, a spring and a button to press down so that the two lengths of cord can be adjusted. Well, I use those to adjust tension on the elastic cord.

I've posted a picture of all the small tools I use to get components off the board. They are primitive but useful.

Robert.

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